1. Field of the Invention
The present invention relates to simultaneous recording and reproduction apparatus wherein audiovisual signals are reproduced from a recording medium while they are recorded thereto.
2. Description of Prior Art
Video cassette recorders (VCR) are very popular in homes. A main use of home VCRs is reserve recording, and recording and reproduction of audiovisual signals are performed in the concept of time-shift.
However, when so-called timer recording is set in a home VCR, the contents of recording cannot be viewed, for example, before a time when the timer recording is completed. That is, the contents of recording cannot be viewed until the recording is completed. In order solve this problem, it is proposed in Japanese Patent laid open Publication 6-14288/1994 that the contents under recording can be viewed freely from the start before the reserve recording is completed. In this reproduction-while-recording, the contents from the start to a recording position can be viewed freely during the recording, and it is called as reproduction-while-recording.
On the other hand, for a DVD-RAM or the like, zone constant linear velocity control (ZCLV) is adopted. In ZCLV, a recording medium is divided in a plurality of areas (zones) in the radial direction, and constant angular velocity recording is performed in a zone. The revolution number is different among the zones, and it is faster at an inner zone. The ZCLV is used because the margin of recording power on recording is limited so that linear velocity has a value in a certain range.
However, the above prior art has the following problems. When an amount of data overflows in a buffer at the recording side, data to be recorded is missed. Further, in reproduction-while-recording, the rates of data write and read for a medium have to be faster than a case where only reproduction is performed. When the reproduction position catches the recording position in high speed reproduction or the like, a user cannot find it. A display image is disturbed when the reproduction position catches up the recording position.
In a recording medium wherein ZCLV or CLV control is used, the optimum revolution number depends on recording position. However, when reproduction-while-recording is performed for such a recording medium, the revolution number may be different between the recording and reproduction position, and it may be necessary to change the revolution number when recording operation is shifted to reproduction operation( (or vice versa). When the revolution number is changed, it takes time for the revolution number to become stable. Thus, it takes time when the recording operation is shifted to the reproduction operation or vice versa. In order to increase the data rate so that the reproduction-while-recording is allowed, the time for the shift has to be shortened as much as possible. Therefore, when it is needed to change the revolution number when the recording operation is shifted to the reproduction operation or vice versa, the data rate in reproduction-while-recording becomes smaller, and it may cause the deterioration of image or sound quality, for example, when audiovisual signals are encoded and recorded.
An object of the present invention is to provide a simultaneous recording and reproduction apparatus wherein an amount of data in a buffer for recording does not overflow.
Another object of the present invention is to provide a simultaneous recording and reproduction apparatus wherein the data transmission rate for the recording medium does not become high even in reproduction-while-recording.
A further object of the present invention is to provide a simultaneous recording and reproduction apparatus wherein a user can note that the reproduction position catches up the recording position in reproduction-while-recording.
A different object of the present invention is to provide a simultaneous recording and reproduction apparatus wherein a display image does not become abnormal even when the reproduction position catches up the recording position in reproduction-while-recording.
A still different object of the present invention is to provide a simultaneous multi-channel reproduction apparatus and simultaneous recording and reproduction apparatus wherein recording and reproduction can be performed at a high data rate when simultaneous recording and reproduction or simultaneous multi-channel reproduction is performed for a recording medium recorded with ZCLV or CLV control.
In a first aspect of the invention, in a simultaneous recording and reproduction, a first buffer memory accumulates a first data stream, a data input device sends the first data stream to the first buffer memory, and a data recorder records the first data stream read from the first buffer memory to a recording medium. On the other hand, a data reproducer which reproduces the first data stream, which has been recorded previously to the recording medium, as a second data stream, a second buffer memory accumulates the second data stream read from the data reproducer, and a data output device which read the second data stream from the second buffer memory. While monitoring an amount of data accumulated in the first buffer memory, a system controller controls the data recorder and the data reproducer to perform recording and reproduction alternately in time, and when an accumulated amount of data in the first buffer memory exceeds a first predetermined-value, the system controller makes the data reproducer stop the reading of the second data stream from the recording medium temporarily and makes the data recorder write the first data stream continuously to the recording medium.
In a second aspect of the invention, in a simultaneous recording and reproduction apparatus, an encoder encodes first input signals to provide a first data stream, a first buffer memory accumulates the first data stream encoded by the encoder, and a data recorder records the first data stream read from the first buffer memory to a recording medium. A data reproducer reads the first data stream which has been recorded previously to the recording medium as a second data stream, a second buffer memory accumulates the second data stream read from the data reproducer, a decoder reads the second data stream from the second buffer memory and encodes it as second signals, and a system controller sets coding rate for the first signals in the encoder. The system controller controls the data recorder and the data reproducer to perform recording and reproduction alternately in time. When the simultaneous recording and reproduction mode is set wherein recording of the first signals and reproduction of the second signals are performed at the same time, and the system controller sets the coding rate in the encoder to be smaller than that in the normal recording mode wherein only the first signals are recorded.
In a third aspect of the invention, in a, simultaneous recording and reproduction apparatus, a system controller, which sets coding rate for the first signals in the encoder, controls the data recorder and the data reproducer to perform recording and reproduction alternately in time. Further, when the simultaneous recording and reproduction mode is set wherein recording of the first signals and reproduction of the second signals are performed at the same time, the system controller sets the coding rate in the encoder so that a sum of recording rate and reproduction rate in a predetermined period is smaller than a predetermined bit rate.
In a fourth aspect of the invention, in a simultaneous recording and reproduction apparatus, a system controller, which sets the coding rate for the first signals in the encoder, controls the data recorder and the data reproducer to perform recording and reproduction alternately in time, and an encoder, which encodes first input signals to provide a first data stream, performs encoding at a variable bit rate and decreases the bit rate for encoding when the first buffer memory is going to overflow.
In a fifth aspect of the invention, in a simultaneous recording and reproduction apparatus, a system controller which monitors recording position of the first data stream to the recording medium and reproduction position of the second data stream from the recording medium, and when the reproduction position catches up with the recording position within a predetermined time, the system controller changes reading of the second data stream by the data reproducer from the recording medium to normal reading mode, or stop mode or temporal stop mode of the reading.
In a sixth aspect of the invention, in a simultaneous recording and reproduction apparatus, a system controller controls the data recorder and the data reproducer to perform recording and reproduction to the recording medium alternately in time. The system controller monitors the recording position of a first data stream to the recording medium and keeps the revolution number which is determined by the recording position of the first data stream while recording or reproduction is performed.
In a seventh aspect of the invention, in a simultaneous recording and reproduction apparatus, a system controller monitors the recording position of a first data stream to a recording medium to control the revolution number of a motor. The system controller controls the data recorder and the data reproducer to perform recording and reproduction to the recording medium alternately in time, and keeps the revolution number which is determined by the recording position of the first data stream while recording or reproduction is performed. The encoder encodes the first signals at a data rate smaller than the maximum data rate realized when data is read at a first recording position where the revolution number for the recording medium becomes a maximum by using a second revolution number most suitable for a second recording position where the revolution number for the recording medium becomes a minimum.
In an eighth aspect of the invention, a simultaneous multi-channel reproduction apparatus used for a recording medium wherein an optimum revolution number of recording depends on reproduction position and at least two data streams are recorded. The simultaneous multi-channel reproduction apparatus comprises a motor which rotates the recording medium, a data reproducer which reads the data streams alternately in time from the recording medium, a system controller which monitors a reproduction position of the data streams on the recording medium by the data reproducer and keeps a revolution on number of the motor during the reproduction by the data reproducer at a revolution number used for reproducing the data stream recorded at an inner position on the recording medium.
An advantage of the invention is that overflow and underflow in buffers for recording and for reproduction is prevented in simultaneous recording and reproduction.
Another advantage of the invention is that recording and reproduction can be performed at a high data rate in simultaneous recording and reproduction and the like.